1. Field of the Invention
The present invention relates generally to infrared thermometers. More specifically, it relates to the probe cover portion of an infrared thermometer, commonly known as ear or tympanic or ear thermometer.
2. Description of Prior Art
Temperature of an object, specifically, of a human or animal, can be measured by the means of thermal conduction or, alternatively, by means of thermal radiation. In the latter case, naturally emanated electromagnetic radiation in the far infrared spectral range is detected by an appropriate sensor, whose output signal is indicative of the surface temperature of an object. A combination of a sensor, electronic circuit and other components form an infrared (IR) thermometer, which is an opto-electronic instrument.
Human or animal body temperature can be measured by placing an optical probe of an IR thermometer into the ear canal or other body cavity.
Nearly all traditional medical contact thermometers, for example, oral or rectal, use the sanitary probe covers. Term "traditional" above and hereafter means contact, non-infrared thermometers and accessories, such as probe covers. In a traditional probe cover, thermal energy (heat) is transmitted by means of thermal conduction, thus, requirements to a probe cover shall comply with the thermally conductive properties of the probe cover material. Various conventional covers for such contact thermometers are described in many patents, for example, in U.S. Pat. No. 4,159,766 issued to Kluge.
For measuring surface temperature of an object without a physical contact, the IR probe is aimed at the area of interest. In medical applications, to measure temperature of a tympanic membrane and the surrounding tissues, the probe is placed into the ear canal. Before the insertion, a probe cover is installed onto the probe to envelop such parts that otherwise might come in contact with the object tissues. The cover shall not only provide a sanitary protection against contamination of the IR probe by ear wax and other soiling compounds, but also it shall possess properties which are critical for the accurate temperature measurement by means of detecting infrared signal. These properties include a good transparency of the front portion of the probe cover in the spectral range of interest (generally, 3 to 15 micrometers), low directional distortion of optical rays, tight manufacturing tolerances, stability of the optical properties during installation onto the probe, long term stability, etc.
As a rule, any prior art IR probe cover employed a thin polymer membrane or film at its optical end (thickness ranging from as little as 0.0005 to as much as 0.0051). The IR radiation has to pass through that membrane before entering the probe and being detected by the IR sensor. In effect, such a probe cover works as an optical filter. Typical materials for fabricating the probe covers are polyethylene, polypropylene, and the copolymers of the above.
Several ways of making the probe covers for the IR medial thermometers are known in art. Generally, all such covers can be divided into two types:
1. The probe covers whose shape is defined during the manufacturing process and remain substantially unchanged while installed onto an IR probe, and PA1 2. The probe covers whose shape is substantially modified during the installation onto the IR probe.
The 1st type is exemplified by U.S. Pat. Nos. 4,662,360, 5,293,862 and 5,179,936 issued to O'Hara et al. which describe a tubular body of the probe cover with a bonded membrane where the tubular body may be injection molded. The tubular body is made of a pliant plastic material. When installed on the IR thermometer probe, the membrane is stressed tight to smooth out the wrinkles. Another examples of the 1st type is the probe covers described in U.S. Pat. No. 5,088,834 issued to Howe and Brown and U.S. Pat. No. 5,163,418 issued to Fraden et al.
The 2nd type of a probe cover is exemplified by U.S. Pat. No. 4,911,559 issued to Meist and Suszinski, which describes a probe cover having a flat polymer film laminated with backing materials. The film stretches around the probe during the installation, thus taking its shape.
Another example of a probe cover is U.S. Pat. No. 5,609,564 issued to Makita et al. where the cover is formed of two layers of film and the positioning ring. The films change shape while enveloping the IR probe during the installation process. U.S. Pat. No. 5,645,350 issued to Jang teaches a wrapping film which is secured on the probe by a fastening cup.
To prevent reuse of a probe cover, Twentier in U.S. Pat. No. 3,878,836 teaches a probe cover ("speculum") having a stretchable portion near the tip which cracks during the installation, thus it can't be reused.
The 1st type of probe covers may suffer from several drawbacks. For examples, the pre-shaped probe covers occupy more space in storage and shall be produced with tight tolerances to minimize negative effects of interaction with the IR probe (such as excessive stretching, tearing of the film, etc.).
Since many probe covers of the 2nd type are fabricated in pliable or flexible shapes or they are laminated with layers of very pliant materials (paper, i.e.), they are more difficult to handle by the user and often require special fixtures or mechanisms for loading onto the IR probe.
Thus, it is an object of the present invention to provide a sanitary barrier between the IR probe and surface of the ear canal.
Another object of the invention is a probe cover which is less sensitive to the manufacturing tolerances.
It is a further object of this invention to provide a probe cover which occupies less space during storage.
It is another object of this invention to provide a probe cover which is less likely to break during the installation.
And the other object of this invention is to provide a probe cover which is easy to install onto the IR probe.